Spoiler effect

The spoiler effect is the effect of vote splitting between candidates or ballot questions[n 1] with similar ideologies. One spoiler candidate's presence in the election draws votes from a major candidate with similar politics thereby causing a strong opponent of both or several to win. The minor candidate causing this effect is referred to as a spoiler.[n 2] However, short of any electoral fraud, this presents no grounds for a legal challenge. The spoiler effect is a problem in plurality voting systems because they enable a candidate to win with less than half of the vote. The problem does not exist in preferential voting or ranked ballot voting systems because voters are allowed to rank their candidate choices, with their vote transferring to their second choice if their first choice does not win, and to their third choice if their second choice does not win, and so on.

The spoiler candidate takes votes away from a more viable[n 3] candidate or candidates, a common effect called vote splitting. Where one opposing candidate is ideologically or politically similar and therefore receives far fewer votes than other opposing candidates to the spoiler candidate, then the vote splitting has a spoiler effect.

In some cases, even though the spoiler candidate cannot win themselves, their influences upon the voters may enable the candidate to determine deliberately which of the more viable candidates wins the election — a situation known as a kingmaker scenario. With a first-past-the-post voting system, this is particularly feasible where a spoiler candidate recommends tactical voting or runs on a false manifesto to bolster the prospects of their secretly preferred winning candidate, which in some jurisdictions and circumstances can amount to electoral fraud.[citation needed]

In a preferential voting system, a voter can feel more inclined to vote for a minor party or independent as their first choice and they can record a preference between the remaining candidates, whether they are in a major or established party or not. For example, voters for a minor left-wing candidate might select a major left-wing candidate as their second choice, thus minimizing the probability that their vote will result in the election of a right-wing candidate, or voters for an independent candidate perceived as libertarian, or simply as the voter prefers that ideology might select a particular libertarian candidate as their second choice, thus minimising the probability of an authoritarian candidate being elected. Approval voting and proportional representation systems can also reduce the spoiler effect.

One of the main functions of political parties is to mitigate the effect of spoiler-prone voting methods by winnowing on a local level the contenders before the election. Each party nominates at most one candidate per office since each party expects to lose if they nominate more than one.[n 4] In some cases, a party can expect to "lose" by "suffering a rival elected opponent" if they nominate more than zero, where two opponents exist and one is considered a candidate they can "work with" — a party may prefer the candidate who would win if the party nominates zero.[n 5]

Thus, empirical observations of the frequency of spoiled elections do not provide a good measure of how prone to spoiling a particular voting method is, since the observations omit the relevant information about potential candidates who did not run because of not wanting to spoil the election.

A possible definition of spoiling based on vote splitting is as follows: Let W denote the candidate who wins the election, and let X and S denote two other candidates. If X would have won had S not been one of the nominees, and if (most of) the voters who prefer S over W also prefer X over W (either S>X>W or X>S>W), then S is a spoiler. Here is an example to illustrate: Suppose the voters' orders of preference are as follows:

33%: S>X>W

15%: X>S>W

17%: X>W>S

35%: W>X>S

The voters who prefer S over W also prefer X over W. W is the winner under Plurality Rule, Top Two Runoff, and Instant Runoff. If S is deleted from the votes (so that the 33% who ranked S on top now rank X on top) then X would be the winner (by 65% landslide majority). Thus S is a spoiler with these three voting methods.

The 2000 U.S. Presidential election is often cited as an example of the spoiler effect. In that election, Al Gore, the Democratic candidate, received more popular votes than George W. Bush, the Republican candidate, but lost in the electoral college. In the state of Florida, the final certified vote count showed Bush with just 537 more votes than Gore.[1] Because Bush defeated Gore in Florida, he won the state, received more votes in the electoral college, and became president of the United States.

Gore supporters argued that had candidate Ralph Nader, a liberal, not run in the election, the majority of the 97,421 votes he received in Florida would have been cast for Gore. Thus, they contend that Nader's candidacy spoiled the election for Gore by taking away enough votes from Gore in Florida to swing the election to Bush. Their argument is bolstered by a poll of Nader voters, asking them for whom they would have voted had Nader not run, which said 45 percent of Nader voters would have voted for Gore, 27 percent would have voted for Bush, and the rest would not have voted.[2]

Nader himself and many of his supporters argued that most Nader voters would either have chosen another minor party candidate or abstained from voting, had Nader not been on the ballot. It should also be noted that all other third party candidates on the ballot in Florida received more than the 537 vote difference between Bush and Gore.[3] Still, some observers began to refer to the spoiler effect as the "Nader effect" after the 2000 election.[4][5][6] A 2006 study found that at least 40% of Nader voters in Florida would have voted for Bush if Nader had not run, while the other 60% would have voted for Gore. The study concluded that this 60% "did indeed spoil the 2000 presidential election for Gore but only because of highly idiosyncratic circumstances, namely, Florida’s extreme closeness."[7]

The Democratic and Republican parties benefit from the spoiler effect created by the existing U.S. plurality voting system, because it deters people from voting for other parties and for independents, in order to avoid "wasting their vote" or causing a spoiler effect. It can also deter 3rd party and independent candidates from running because by doing so they could split the vote thereby causing an election result they do not want.

These are third-party candidates who have been accused of denying victory to a major nominee in U.S. Presidential Elections; a notable case among these is the 1912 election, where Progressive Party candidate Theodore Roosevelt won just under 700,000 votes more than did the Republican incumbent, William Howard Taft, and thus it could be said that Taft was the spoiler for Roosevelt in that election.

In 1994, moderate Republican Marshall Coleman ran for the U.S. Senate as an independent, receiving over 11 percent of the vote in an election where Democrat Chuck Robb defeated Republican nominee Oliver North by only three percent of the vote.

In 2010, Green Party candidate Bill Scheurer ran for Illinois 8th Congressional District against Democratic incumbent Melissa Bean. Republican Joe Walsh won the election in a surprising upset with only a 291-vote (0.1%) difference with Bean, while Scheurer received 6,494 votes (3.2%).

Likewise, in France, the 2002 presidential elections have been cited as a case of the spoiler effect: the numerous left-wing candidates, such as Christiane Taubira and Jean-Pierre Chevènement, both from political parties allied to the French Socialist Party, or the three candidates from Trotskyist parties, which altogether totalled around 20%, have been charged with making Lionel Jospin, the P.S. candidate, lose the two-round election in the first round to the benefit of Jean-Marie Le Pen, who was separated from Jospin by only 0.68%. Some also cite the case of some circumscriptions where, although the right and the far-right were voted for by more than half of the voters, the left list still won the election, and accused the Socialist party of benefiting of this phenomenon.

In sports, the "spoiler effect" refers to a similar phenomenon, in which a team or individual has been eliminated from the possibility of reaching the postseason, but affects the playoffs or finals anyway by beating a more successful team or individual before the end of the season. For example, a baseball team that is ten games out of contention for a playoff berth could defeat a team that has a playoff berth several times. This could cause the would-be playoff team to be passed by in the rankings by the team directly behind it before the final positions at the end of the season are determined.

In individual participant sports, such as automobile racing, a racer with no hope of obtaining a championship title could prevent a racer with a chance at the title by defeating them, preventing the contending racer from earning critical points toward winning the title. Instead, the title would go to the contender directly behind him in the rankings, provided that second-tier racer is close enough to surpass and they win their own competition.

^A term designed to appeal to a wider section of the public as a result of the widespread, often national support of political parties.

^More viable by common public sentiment which may sometimes be indicated in opinion polls.

^For example, if the Democrats had nominated both Hillary Clinton and Barack Obama for U.S. President in 2008, it would have allowed the Republican candidate (John McCain) to easily win; the voters who preferred both Clinton and Obama over McCain could not have been relied on to solve the strategy coordination problem on their own.